Three datasets were used for this analysis. The primary data set was taken from a previously reported experiment on the effects of 500 U/ml pegylated interferon alpha and 10 μg/ml ribavirin on peripheral blood monocytes (PBMC) in culture [16]("IFN data"). PBMC were isolated from different individuals and aliquots exposed to interferon, ribavirin, both or neither for 24 hours in culture. The individual samples were processed and each hybridized to a HGU133A GeneChip® following standard Affymetrix protocols. The previous analysis of the IFN data determined that the ribavirin had no detectable effect on gene expression [16]; therefore, to increase the power to detect changes the arrays from the no treatment group and the ribavirin only group were combined to create a control group of 10 samples, and the interferon and interferon + ribavirin groups were combined to create an interferon-treated group of 10 samples [16].
